I've had this problem before, twice, once in Windows and once in Linux(don't ask).
The problem was missing font. Are you sure you installed the tahoma font right? Drag it to your desktop, right click, select install(win vista/7). It should appear in C:\WINDOWS\Fonts as Tahoma Normal(Norwegian windows) or tahoma.ttf. If it's still not working, delete/rename the garrysmod folder in your steamapps/<user name> folder, then try start the game. Still failing? Then something is terribly wrong D:

About the keyvalue errors, those are broken addons. Check if they contain an info.txt file. If not, delete them, or reinstall them properly.

I've had this problem before, twice, once in Windows and once in Linux(don't ask).
The problem was missing font. Are you sure you installed the tahoma font right? Drag it to your desktop, right click, select install(win vista/7). It should appear in C:\WINDOWS\Fonts as Tahoma Normal(Norwegian windows) or tahoma.ttf. If it's still not working, delete/rename the garrysmod folder in your steamapps/<user name> folder, then try start the game. Still failing? Then something is terribly wrong D:

About the keyvalue errors, those are broken addons. Check if they contain an info.txt file. If not, delete them, or reinstall them properly.

I don't see how the Tahoma font could just disappear.. I use it in GIMP a lot.

I love you Black Razor 88 and I Love you AlfieGroove I have been trying everything to fix this same issue and after 2 weeks i just found this and the fonts worked for me too. I love you all. Thank you.

guys i did put in the dxlevel thing and restarted gmod but i can still not see servers please i beg i need help!

Calmly explain the problem without leaving out any detail. I'm guessing from reading your post that either you have the same problem as the person who created the thread, or that no servers are showing up in the server browser.